Implement erasable Enum Annotations #61414
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… to Enum Literals)
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| @@ -822,6 +826,9 @@ function createBinder(): (file: SourceFile, options: CompilerOptions) => void { | |||
| if (isNamedDeclaration(node)) { | |||
| setParent(node.name, node); | |||
| } | |||
| if (isEnumLiteralExpression(node) && symbol.valueDeclaration === node.parent) { | |||
| @@ -16706,6 +16711,10 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker { | |||
| links.resolvedSymbol = unknownSymbol; | |||
| return links.resolvedType = checkExpressionCached(node.parent.expression); | |||
| } | |||
| // `var MyEnum: enum = { FirstValue: 1, SecondValue: 2 }` should resolve to a union of the enum values. | |||
| if (isEnumTypeReference(node) && isVariableDeclaration(node.parent) && node.parent.initializer && isEnumLiteralExpression(node.parent.initializer)) { | |||
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FIXME: isEnumLiteralDeclaration(node)
| @@ -44128,7 +44140,7 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker { | |||
| checkClassNameCollisionWithObject(name); | |||
| } | |||
| } | |||
| else if (isEnumDeclaration(node)) { | |||
| else if (isEnumDeclaration(node) || (isVariableDeclaration(node) && node.initializer && isEnumLiteralExpression(node.initializer))) { | |||
| const nonexist: E1 = E1.NonexistingShorthand; // ok | ||
| const exist: E1 = E1.ExistingShorthand; // ok | ||
| const ival: E1 = E1.Int; // ok | ||
| const sval: E1 = E1.String; // ok |
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Does this implementation support types for individual variants? In other words, would the following work?
const exist: E1.ExistingShorthand = E1.ExistingShorthand; // ok
const ival: E1.Int = E1.Int; // ok
const sval: E1.String = E1.String;
I looked through the PR, but did not see code handling it or tests for this. It seems however to delegate to the existing enum handling in some places so I assume that it should work. I would appreciate a confirmation, thank you.
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I've made an effort to add a few of these tests (and they seem to be working, although it is a bit loose with accepting a wider number type for a unique numeric enum value. I believe that's normal for TS enums, though), but mostly I was focused on getting the invariant checks working. Thanks for the suggestion.
….ts for individual members as types
In order to meet the goal of allowing "erasable" syntax only, which can be trivially converted to JS by removing type annotations, as described in #60790, including input from the TypeScript team to prefer the annotation to the "as enum" syntax.
This permits emitting code by simply erasing the Type Annotation. The TypeChecker sees references to the variable as a reference to an Enum-like type.
There are currently a few remaining obvious issues, for instance comments surrounding EnumMembers in the source are omitted from the emitted JS.
CC @nicolo-ribaudo @romulocintra